Power transmission devices of the type to which the present invention relates are characterized by the fact that they present a power input end and a power output end. Some type of power means, for example for activation by means of a pressure medium or an electric current, is arranged at the power input end. The power which the power means exerts on the power transmission device is transmitted by the device to the power output end for driving, for example, a machine tool, a displacement device or other arrangement which requires a displacement force for its operation. The purpose of the power transmission device is thereby to transmit the power from the power member to the driven device by converting the movement to another relationship between power and displacement than that which the power member can produce and/or controlling the movement or distributing it.
The present case relates to a power transmission device for a preferably linear movement and a reciprocal movement, that is to say not principally a rotating movement. The movement is thus restricted to a certain stroke length or displacement path in a to and fro movement. The term linear is not necessarily to be understood as a movement along a straight line; the movement can also follow a curved line and can even comprise a restricted to and fro rotational movement.
Devices of this type are previously known from many applications. By way of example, such applications include shears for plate and other material, edge-pressing machines, rods for parallel transfer or scraping, and members in automated assembly machines, etc. The knives in cutting machines or the press tool in edge pressing machines can typically be held in a carriage or on arms for parallel oscillatory movement and thereby driven by compressed air or hydraulic cylinders or electromagnets. The latter means accordingly form the power member and the power transmitting device is formed by the carriage or arm system which guides and distributes the force along the entire length of said tool. In certain cases a gear reduction takes place to achieve a greater force at the output device than the power member is capable of developing or, alternatively, an increasing of the movement path with a loss of force exertion.